1. Technical Field
The present invention relates to a technique for controlling the rotation angle of a retardation plate in a projector.
2. Related Art
Light source devices using a solid-state light source such as a laser diode have been known. In such light source devices, light of a certain wavelength band which is output from the solid-state light source is separated by a polarization separation mirror. One beam of light separated is guided to a phosphor, as excitation light, and the phosphor emits light of a wavelength band different from that of the solid-state light source. The light which is output from the phosphor is synthesized with the other beam of light separated, and is output as light including more wavelength band components.
Such light source devices have a problem in that a white balance of light to be output shifts due to a change in the characteristics of the solid-state light source or the phosphor over time. On the other hand, for example, JP-A-2015-106130 discloses a light source device that compensates for a change in color balance associated with a change over time during its use.
In the technique disclosed in JP-A-2015-106130, a change in color due to a deterioration in a light source is measured when the brightness of a light source is set to a specific value, and a color balance is adjusted by rotating a retardation plate in accordance therewith. However, in a case where the retardation plate is controlled so as to maintain the color balance, there is a problem in that, as a result, the brightness changes.